One of the reasons would be the hatred that the West created for Islam, influenced by 9/11. The media fueled the terrorist / Muslim stereotype. People acquitted this stereotype, deceived by their xenophobia and hatred of immigrants (with the question that they are the causes of unemployment). In addition to our historical Christian indoctrination; the supremacy of Christianity in the West made it possible to revive the period of the great crusades as "positive" humanity.
As commented earlier, terrorism is everywhere, regardless of belief, country or race. Islam is not, and has never been synonymous with terrorism; what in fact exists, are radical strands, just as in Christianity itself, Protestantism, or any other ideology. And what actually happens, is the mediatic reporting of these cases of terrorism, extolling the aforementioned stereotype.
Sorry for some writing mistakes, I'm Brazilian.